1. Field of the Invention
This invention relates to a heat exchanger for use in a vehicle air conditioning system, and more particularly, to methods for connecting a plurality of heat transfer tubes in such heat exchangers.
2. Description of the Prior Art
FIG. 1 shows a conventional heat exchanger used in an air conditioning system, for example, an evaporator or a condenser. In FIG. 1, heat exchanger 10 comprises upper tank 11, lower tank 12, and heat exchanger core 13 disposed between upper tank 11 and lower tank 12. Heat exchanger core 13 comprises a plurality of heat transfer tubes 14 spaced from one another and disposed in parallel to one another. Upper tank 11 comprises upper wall 11a and lower wall 11b which are united with each other. Upper tank 11 is divided into three chambers, such as first upper chamber 18, second upper chamber 19, and third upper chamber 20, by partition portion 11c. Lower tank 12 is divided into two chambers, such as first lower chamber 21 and second lower chamber 22, by partition portion 12c. Lower wall 11b of upper tank 11 and upper wall 12a of lower tank 12 are provided with a plurality of connection holes 11d and a plurality of connection holes 12d, respectively, for connecting a plurality of heat transfer tubes 14 and, thereby, placing tanks 11 and 12 in communication. Inlet pipe 15 and outlet pipe 16 are connected to upper tank 11.
Referring to FIG. 2, for example, a heat exchanger medium is introduced via inlet pipe 15 into first upper chamber 18 and flows down through heat transfer tubes 14 to first lower chamber 21. It then flows back to second upper chamber 19 through heat transfer tubes 14. Further, the heat exchanger medium again flows from second upper chamber 19 through heat transfer tubes 14 and reaches second lower chamber 22. It then flows back to third upper chamber 20 through heat transfer tubes 14. When the heat exchanger medium flows through heat transfer tubes 14, heat exchange occurs between the heat exchanger medium and air flow 17 passing over heat transfer tubes 14, as shown in FIG. 2.
Generally, heat exchanger 10 uses numerous heat transfer tubes 14 to obtain a high heat exchange efficiency. In assembling processes, however, numerous heat transfer tube 14 are inserted, one by one, into connection holes 11d of upper tank 11 and connection holes 12d of lower tank 12, respectively, as shown in FIG. 3. This step of the assembly processes is both complicated and time consuming. As a result, the operational productivity of the assembling processes is reduced.